FOR GEORGE W. BUSH, as for any president seeking a second term, the party's convention presents a different, and in many ways more difficult, task than that facing his opponent. At the Democratic convention, Sen. John F. Kerry had the job of introducing himself to voters and convincing them that he has the capacity to lead the nation. But Mr. Kerry, like any challenger, enjoyed the benefit of writing his convention script on a relatively clean slate; his promises and his vision can't be judged against the cold reality of whether he was able to implement them or how he has governed.

Mr. Bush, by contrast, is a known commodity with a known record. For him, the convention that begins in New York today is not a nationally televised job interview but rather a four-day performance review. From inside Madison Square Garden, a positive assessment is preordained. Yet Mr. Bush confronts a divided and skeptical electorate, with polls showing a slim majority of voters believing that the country is on the wrong track and in need of a change. This week's gathering represents the opportunity for Mr. Bush to change their minds.

In looking back to four years ago, we are struck by the ways in which the Bush presidency has been different from the way it was originally sold to the country. Mr. Bush promoted himself to voters in the 2000 campaign as a bipartisan uniter, not a divider, but in office he has too often embraced a my-way-or-the-highway style of governing that has served to polarize voters. Mr. Bush the candidate promised a "humble" foreign policy; Mr. Bush the president has too often adopted a highhanded approach to the world that alienated allies. As the convention opens, Mr. Bush seems interested in presenting his, and his party's, kinder, gentler side -- GOP moderates dominate the list of prime-time speakers -- but this image promises to be a tougher sell than it was four years ago.

In some areas, Mr. Bush has demonstrated commendable flexibility in adapting to changing circumstances. The candidate who exuded a crabbed view of America's leadership role and demeaned the notion of "nation-building" was transformed by the attacks of Sept. 11, 2001, into a president with an activist, if controversial, vision of American power. In other matters, though, particularly his insistence on tax cuts, Mr. Bush has stubbornly and recklessly hewed to the same policy despite a dramatically different economic situation -- a surplus that turned out to be a mirage -- and new demands placed on the treasury by the war on terrorism.

In making the case that his first-term performance has earned him another four years, Mr. Bush's central focus will be his conduct of the war on terrorism. On this subject, he faces the challenge of justifying not only the wisdom of his decision to invade Iraq but his conduct of the war. During the Democratic convention in Boston, we faulted Mr. Kerry for failing to credit some of the administration's achievements in Afghanistan and Iraq and failing to reaffirm his commitment to completing the task of helping build democracy in Iraq.

What we would hope for from Mr. Bush is not simply chest-thumping about the bene- fits of dislodging the Taliban and overthrow- ing Saddam Hussein but a more candid reflection on the ways those campaigns have fal- len short: the unanticipated insurgencies, the inadequacy of postwar preparations and the shocking abuses of Iraqi detainees. A con- vention speech isn't a confessional, but Mr. Bush would have more credibility in arguing that he should be given more time to finish the jobif his self-assessment reflected some of his administration's shortcomings as well as its achievements.

The convention is also a time for Mr. Bush to fill in what has been the missing ingredient of his re-election campaign: what he would do with the next four years. There are whispers of bold new proposals in development -- broad tax reform, perhaps, or a fleshing out of Mr. Bush's vision of an "ownership society" -- but in truth the fiscal irresponsibility of the president's first term has hobbled his ability to enact his policies in a second. Mr. Bush's father spoke of having more will than wallet; the current president, during his first term, demonstrated little will to take on reforming Social Security and Medicare, and now he has no wallet either. How the president deals with that problem is also an important subject for discussion in New York this week.